The present invention relates to laser systems and particularly a method and apparatus for laser marking objects at high speed.
It is known that food and medicinal products that are susceptible to spoilage or effectiveness often have a use by or expiration date that is printed on the items themselves or on the packaging of the items so a purchaser or potential user of the goods can make a judgment of whether the product is current or outdated. This is particularly important for some food products, which can become dangerous, with chicken eggs being a prime example because of the threat of salmonella poisoning.
It is for that reason that eggs are commonly packed in cartons that have expiration dates printed on the carton. A problem with this type of dating is that consumers often remove the eggs from a carton and put them in a special holders of their refrigerator and therefore lose the important expiration date information. Although it is not believed to be a widespread practice, there have been instances where establishments have removed eggs from one printed carton and placed in another having a later expiration date which can lead to usage beyond the date by which salmonella bacteria can develop into a dangerous condition. While there have been attempts to print expiration dates on the eggs themselves with ink jet printing or other type of marking, the permanency of such printed information is suspect and can often be removed.
A particularly desirable way in which to mark eggs is to use a laser to etch an expiration date and other information on the shell of the egg which results in a permanent marking that cannot be removed from the egg itself. Such marking is described in a patent application entitled METHOD AND APPARATUS FOR MARKING AN EGG WITH AN ADVERTISEMENT, A FRESHNESS DATE AND A TRACEABILITY CODE, having Ser. No. 11/333,580, filed Jan. 17, 2006, which is specifically incorporated by reference herein.
Because billions of eggs are produced annually in the United States alone, marking even a fraction of such numbers of eggs is a formidable undertaking. A large majority of eggs sold in the United States are produced in only a few hundred locations. At these locations, grader systems clean, candle, grade and pack eggs in large volumes. High volume grader systems generally have from two to six rows of eggs that are conveyed through the various stages of the grading system and can currently process up to 175,000 eggs an hour.
Since marking of eggs must be done during this grading process to be economical, it is necessary to mark the eggs very rapidly without slowing down the speed of operation of the grader system. Thus, the marking operation must necessarily occur within a very small time and physical size window. Because of time and physical size constraints, the amount and complexity of indicia that can be marked on the eggs is limited, and the laser marking apparatus must be sized to fit in the grader in a manner which does not interfere with the normal operation of the grader.